Mathematical Physics
M-theory
M-theory is a proposed framework in theoretical physics that unifies the five consistent versions of superstring theory through dualities and is expected to have an eleven-dimensional low-energy limit described by eleven-dimensional supergravity. First articulated by Edward Witten in 1995, the framework incorporates extended objects such as two- and five-dimensional branes and has seen nonperturbative formulations proposed via matrix theory and holographic dualities.
Spacetime
Spacetime is the four‑dimensional geometric framework that unifies three dimensions of space with one of time, underpinning modern theories of motion, gravitation, and cosmology. Formulated in its modern form in the early 20th century through the work of Albert Einstein and Hermann Minkowski, spacetime is modeled mathematically as a Lorentzian manifold whose metric determines intervals, causal structure, and gravitational dynamics. It provides the setting for special relativity in flat Minkowski space and for general relativity, where mass–energy curves spacetime and guides the motion of matter and light.